Distance measurement technology is applied extensively in various fields such as aerial range finding, nautical range finding, industrial range finding, and camera range finding. The image-processing-based depth measurement technologies disclosed in associated academic papers and patents include the following two types of methods:                1. Improvements in system architecture: For example, the U.S. Pat. No. 5,361,127 “Multi-image single sensor depth recovery system” by Daily and Michael J. comprises a sensing device, a multi-faceted lens, and a multi-image stereo depth analysis means. The sensing device has a sensing plane. The multi-faceted lens has a multiplicity of refractive facets for directing radiation directly from an object to said sensor plane. The multi-image stereo depth analysis means analyzes the data stream from said sensing device and determines the depth of said object. Namely, the patent improves the lens structure and hence being able to project multiple images corresponding to the object to the sensing plan.        2. Improvements in algorithm: For example, the U.S. Pat. No. 6,490,364 “Apparatus for enhancing images using flow estimation” by Hanna, et al. provides an apparatus for enhancing images comprising a first imaging device, a second imaging device, and an image processor. The first imaging device produces images at a first resolution. The second imaging device produces images at a second resolution. The image processor aligns said images from said first and second imaging devices to form a plurality of aligned images and computes the parallax of the plurality of aligned images for giving the depth. The first and second imaging devices are cameras, respectively, for acquiring the images of an object. The image processor computes the offset between said two images for giving the parallax corresponding to the object. For ensuring measurement accuracy, multiple images can be acquired from the object, especially when the object is covered.        
No matter what kind of technologies described above, two or more images of an object must be acquired first then the corresponding points of the images can be computed for reconstructing the depth information of the object. Nevertheless, current technologies are limited by high hardware costs owing to high circuit complexity or high precision of optical structures, as well as by complex algorithms of image processing. These prevent proper promotion in development and applications.
Accordingly, the present invention provides an apparatus and a method for measuring the depth of an object in a scene, which can provide better computing efficiency with simpler circuit. Hence, the problems described above can be solved.